It is thought that the sjK>res seldom spread and cause infection during 

 the summer months unless under favourable weather conditions i.e., very 

 \vet. We believe that infection does not become serious until early in 

 October or about the time the fall rains bring conditions favourable to the 

 sj i read of the disease and its development. By making a careful examination 

 of the young wood a month or so after that, we have found the disease 

 started in the form of small, round, dark-coloured spots. During November 

 and December most of the infection seems to take place, as it is after these 

 months that nearly all the si>ots that develop into canker are noticed. 



Injuries on the bark make a favourable place for the spore to lodge, 

 germinate, and gain entrance to the underlying cell-structures. From obser- 

 vations taken it seems i>ossible for the spore to gain entrance through 

 uninjured and healthy bark, as cankers have been found starting where 

 there has been no apparent previous injury. After germinating and gaining 

 entrance, it works on the outer layers of wood for a short time and then 

 gradually works its way through to the cambium layer, when it develops very 

 rapidly. On cutting into a young canker you will sometimes find that it 

 has developed in a much larger area than is indicated on the bark, and as 

 it continues to grow this condition changes, making the mature canker, 

 showing the same area of attack on the surface as in the underlying layers. 



In the young trees up to three or four years of age all parts seem to 

 be attacked without favour. As the tree grows older and the bark becomes 

 harder, we find the principal parts of attack are in the young wood. It 

 has also been noticed that the disease often starts around crotches, especially 

 where the crotch is such that it will hold foreign material. On that account 

 these bad crotches (crotches leaving the main trunk at a sharp angle) should 

 be avoided as far as possible when starting the young head. Anywhere from 

 one to hundreds of these cankers have been found in trees varying from 

 ty to inches in length and % to 4 inches in width. Where the cankered 

 area is larger, this is often due to two cankers growing together. 



CONTROL. 



The same general principles of control of fungus pests in the orchard 

 are applicable here. The spores of the disease require moisture to germinate. 

 so 5 t is advisable to select a site for the orchard (this has reference princi- 

 pally to the Coast districts) and handle the trees so to guard, as far as 

 IMissible. against moisture remaining on the tree longer than necessary. 

 Ixw lands should be avoided, not only on account of more danger from 

 frosts, but there is little circulation of air there, especially at night, and 

 as a consequence moisture will remain on the tree longer than where the 

 orchard is on a side-hill or on higher ground. (Jood circulation of air iu 

 the orchard will keep the tree drier and in a condition less favourable to 

 flu- attack of the fungus. On a side-hill, even on a still night, air will circu- 

 late down the slopes, as it always seeks the lowest levels. 



Prune so as to permit good air-circulation and plenty of light. This 

 is not only valuable in making conditions unfavourable for the development 

 of the disease, but is necessary for the production of clean, well-coloured, 

 and uniform fruits. 



Keep the trees in a healthy condition by proper cultural methods. It is 

 noticeable that we find the disease worst in poorly cared-for and neglected 

 orchards. This does not prove that, it will attack a poorly cared-for tree more 

 readily than it will a healthy one. but that conditions for attack are more 

 favourable. Injuries from insects and fungous diseases are found in greater 



